Fixed behaviours and migration in parasitic flatworms

This paper considers how fixed behaviours may play a role in post-larval migrations of Entobdella soleae. A general argument is that a shift away from the paradigm of orientation is required to elucidate the mechanisms that parasites use to navigate on the surface of their hosts. Some migrations may rely on fixed behaviours (genetically programmed stereotyped behaviours) that often evolve under predictable environmental conditions with reliable signals. In turbulent and stochastic free-living environments, homeostatic hosts present very predictable topological substrates and physico-chemical characteristics to their parasites. Over the course of evolution on these predictable host substrates, adaptive behaviours in the parasites can become fixed. Examples of endoparasite migration behaviour, particularly that of the common liver fluke, Fasciola hepatica, will be used to develop an approach based on the perceptual worlds of migrating parasites. An important conclusion is that multi-disciplinary approaches, firmly rooted in an understanding of each parasite's natural history, are requisite to successful interpretation of migration behaviours on the host.     

Hierarchical Categorical Perception in Sensing and Cognitive Processes

This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical perception (CP) and categorical sensing (CS) in order to extend the CP framework to all communication processes in living systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing semiotic freedom observed in biological and cognitive systems.

Role of Utility and Inference in the Evolution of Functional Information

Functional information means an encoded network of functions in living organisms from molecular signaling pathways to an organism’s behavior. It is represented by two components: code and an interpretation system, which together form a self-sustaining semantic closure. Semantic closure allows some freedom between components because small variations of the code are still interpretable. The interpretation system consists of inference rules that control the correspondence between the code and the function (phenotype) and determines the shape of the fitness landscape. The utility factor operates at multiple time scales: short-term selection drives evolution towards higher survival and reproduction rate within a given fitness landscape, and long-term selection favors those fitness landscapes that support adaptability and lead to evolutionary expansion of certain lineages. Inference rules make short-term selection possible by shaping the fitness landscape and defining possible directions of evolution, but they are under control of the long-term selection of lineages. Communication normally occurs within a set of agents with compatible interpretation systems, which I call communication system. Functional information cannot be directly transferred between communication systems with incompatible inference rules. Each biological species is a genetic communication system that carries unique functional information together with inference rules that determine evolutionary directions and constraints. This view of the relation between utility and inference can resolve the conflict between realism/positivism and pragmatism. Realism overemphasizes the role of inference in evolution of human knowledge because it assumes that logic is embedded in reality. Pragmatism substitutes usefulness for truth and therefore ignores the advantage of inference. The proposed concept of evolutionary pragmatism rejects the idea that logic is embedded in reality; instead, inference rules are constructed within each communication system to represent reality, and they evolve towards higher adaptability on a long time scale.     

Adipositas – eine Bürde der Evolution?

Obesity – a consequence of evolution? The high obesity rates are the result of a dramatic mismatch between current environment and a human body evolved in the environment of our evolutionary adaptedness. Various evolutionary hypotheses try to explain this relationship. Natural and sexual selection shaped our gene pool towards an optimal adaptation to these environments and life circumstances. Our recent obesogenic environment differs dramatically from that in which we evolved.     

Structural aspects of arboreality in titi monkeys (Callicebus moloch)

In nature titi monkeys spend virtually all of their time in trees. Preferences for certain heights above the ground or for trees per se are probably not, however, the immediate causes of this behavior, for animals housed in a large field cage containing many trees spend most of their time on a low-altitude artificial runway system. Further, the animals are not necessarily reluctant to touch the ground. To investigate the importance of perceived substrate structure as a determinant of arboreality, individuals were given opportunities to descend from their home runway and travel to food placed nearby on the ground. The animals travelled along a schematic model of a tree branch rather than across open ground when given a choice of these substrates, but they readily crossed the open ground when it was their only travel option. When the schematic model increased substantially in length and no longer provided a short route to food, it was still the preferred substrate. The results suggest that an abstract representation of a tree branch attracts and guides locomotion in titis, and that responsiveness to substrate characteristics contributes to arboreality in this species.     

Umwelt Transitions: Uexküll and Environmental Change

What role does environmental change play in Jakob von Uexküll’s thought? And what role can it play in a up-to-date Uexküllian framework? Admittedly, in hindsight it appears that the Umwelt theory suffers from its reliance on Uexküll’s false premise that the environment (including its mixture of species) is generally stable. In this article, the Umwelt theory of Uexküll is reviewed in light of modern findings related to environmental change, especially from macroevolution. Uexküll’s thought is interpreted as a distinctive theory of phenomenology—an ‘Uexküllian phenomenology’—characterized by an assumption of the (in the realm of life) universal existence of a genuine first person perspective, i.e., of experienced worlds. It is suggested that acknowledging this distinctiveness is critical for eco-phenomenology as well as for biosemiotics; the latter of which can only thus thrive as a true ‘semiotics of being’, rather than a mere ‘semiotics of functioning’.     

Logistisches wachstum in fluktuierender umwelt

The logistic differential equation with generalized nonlinearity and time-dependent coefficients can be solved explicitly. The results of Sonneveld and van Kan can be carried over to the case of not necessarily periodic coefficients.